泛型事件，或基于泛型类型的引发事件. [英] Generic event, or raise event based on generic type.

问题描述

在昨天的讨论之后，我正在研究可以在应用程序范围内订阅的Singleton的"Notifier"类的想法.为了通过允许在事件args中传递任何类型来使其更有用，我认为泛型将是一个好主意.通用TEventArgs<T> : EventArgs被设置并且可以正常工作

单例的通用类是不可能的，因为这样实例将被绑定到单个类型，所以我得到了一个通用方法，该方法反过来调用
protected virtual void OnNotify<T>(TEventArgs<T> e) { }

因为类本身不是通用的，所以我无法弄清楚如何创建通用事件
public event EventHandler<TEventArgs<T>> Notification;
，因为T不是尚未定义.有办法吗?

是否失败?是否可以基于OnNotify方法中T的类型引发特定类型的事件，该事件具有硬编码类型(例如public event EventHandler<TEventArgs<int>> Notification)
并使用e参数?

我可能在这里吠叫了错误的树，但我确定应该可以！

After a discussion yesterday I''m playing around with the idea of a Singleton ''Notifier'' class that can be subscribed to application wide. To make this more useable by allowing any type to be passed in event args, I figured generics would be a good idea. The genric TEventArgs<T> : EventArgs is set up and working fine

A generic class for the singleton is not possible as then the instance would be tied to a single type so I''ve got a generic method that in turn calls
protected virtual void OnNotify<T>(TEventArgs<T> e) { }

Because the class itself isn''t generic, I can''t figure out how to create a generic event
public event EventHandler<TEventArgs<T>> Notification;
as T isn''t yet defined of course. Is there a way?

Failing that, is it possible to raise a specific event that has the type hard coded
(e.g. public event EventHandler<TEventArgs<int>> Notification)
based upon the type of T in the OnNotify method and use the e parameter?

I could be barking up the wrong tree here but I''m sure it should be possible!

推荐答案

我认为我得到了您的第二个想法的有效版本.诀窍是使用事件访问器.字典中value参数的类型应该是一个列表-我采取了一条捷径，因此每种类型仅适用于一个订户:)

I think I got a working version of your second idea. The trick was to use event accessors. The type of the value parameter in the Dictionary should be a list - I took a shortcut so it works only for one subscriber per type :)

<br />        class TEventArgs<T> : EventArgs { public T Value { get; set; } }<br /><br />        class Test<br />        {<br />            Dictionary<Type, object> d = new Dictionary<Type,object>();<br /><br />            public event EventHandler<TEventArgs<int>> MyEvent1<br />            {<br />                add<br />                {<br />                   d.Add(typeof(int), value); <br />                }<br /><br />                remove<br />                {<br />                    d.Remove(typeof(int));<br />                }<br />            }<br /><br />            public event EventHandler<TEventArgs<string>> MyEvent2<br />            {<br />                add<br />                {<br />                    d.Add(typeof(string), value);<br />                }<br /><br />                remove<br />                {<br />                    d.Remove(typeof(string));<br />                }<br />            }<br /><br />            public void OnNotify<T>(T t)<br />            {<br />                EventHandler<TEventArgs<T>> del = (EventHandler<TEventArgs<T>> )    d[t.GetType()];<br />                del(this, new TEventArgs<T>() { Value = t });<br />            }<br />        }<br /><br />        static void Main()<br />        {<br />            Test t = new Test();<br />            t.MyEvent1 += new EventHandler<TEventArgs<int>>((sender, args) => Console.WriteLine(args.Value + 1));<br />            t.MyEvent2 += new EventHandler<TEventArgs<string>>((sender, args) => Console.WriteLine(args.Value.Trim()));<br /><br />            t.OnNotify(23);                // Prints 24<br />            t.OnNotify("Senthil Rocks  "); // Prints Senthil Rocks<br /><br />

和remove访问器非常相似，但是编译器不喜欢事件声明是否具有通用参数.

The code inside the add and remove accessors is very similar, but the compiler doesn''t like if the event declaration has a generic parameter.

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